1. Field of the Invention
The invention relates to a cleaning device for printing machine cylinders. The device includes a clean cloth spindle and a dirty cloth spindle between which the cloth is driven and contacts a cylinder to be cleaned. The invention concerns bearing units for the spindles including novel bearing bush arrangements.
2. Prior Art
These devices are known from practice. Further prior art is known from the following publications:
U.S. Pat. No. 5,519,914,
DE 197 25 505 A1,
EP 0 539 771 A1,
EP 0 795 403 A1,
DE 295 16 348 U1,
U.S. Pat No. 4,344,361=
DE 30 05 469 C2,
DE 43 05 153 C1,
DE 40 27 505 A1,
DE 43 19 258 A1,
DE 42 11 310 A1,
DE 41 35 892A1,
DE 195 43 518 A1.
Known printing machine cylinder cleaning devices of this type normally form a structural unit which is known as a xe2x80x9cwashing beamxe2x80x9d. Such a washing beam is moveable between a basic position, in which it is at a distance from the printing machine cylinder to be cleaned, and a washing position, in which a portion of a washing-cloth is pressed onto the outer surface of the printing machine cylinder by a pressure element of the washing beam. The washing cloth is in each case then transported further on by the amount of a predetermined cloth portion, so that a new clean washing-cloth portion is opposite the printing machine cylinder when the washing beam is moved back from the washing position into the basic position. The washing cloth is transported further on this way by means of a freewheel drive on the dirty-cloth spindle. The freewheel drive acts in the manner of a ratchet so that during the movement of the washing beam in the direction from the washing position to the basic position, the drive drives the dirty-cloth spindle, but, during the reverse movement from the basic position to the washing position, the drive rotates idly in relation to the dirty-cloth spindle, that is without corotating the spindle. The washing cloth on the clean-cloth spindle may be dry and may be moistened with fluid on its path between the clean-cloth spindle and the pressure element or directly at the pressure element by a moistening device. It is also known to have a moist washing cloth on the clean-cloth spindle. Within the scope of the present invention, the washing cloth is called a xe2x80x9ccleaning clothxe2x80x9d, because the invention can also be used for dry cleaning cloths.
Particularly when the cloth movement starts, the dry-cloth spindle does not rotate more quickly than the dirty-cloth spindle can receive the cleaning cloth and does not follow on when the dirty-cloth spindle stops, which would result in a loosening and sagging of the cleaning cloth and consequently in the risk of the loose washing cloth being picked up by the printing machine cylinder and carried along. It is know to provide the clean-cloth spindle with a sustained-action brake. This consists, in the prior art, of a brake lining which is prestressed radially against a bearing bolt by a screw via a spring. The disadvantage of this is that even a small rotational movement of the screw may generate too strong or too weak a braking action. A small change in screw excursion results in a pronounced variation in braking force. The braking force therefore cannot be set with sufficient accuracy, and it changes relatively sharply in the event of wear of the brake lining.
The bearings of the clean-cloth spindle and of the dirty-cloth spindle each have a bearing bush which is provided at one end with a flange. The bearing bush and the flange together consist of a one-piece part. To produce this, a relatively large piece of material is necessary, from which a large amount of material has to be removed by cutting in order to form the bush. The flange has three passage holes for receiving screws, by means of which the bearing element consisting of the bearing bush and flange can be screwed to a side part of the cleaning device. In this side part locating bores are formed, into which the bearing bush is fitted. Furthermore, triangular depressions for receiving the triangular flanges are formed around the locating bores in the side parts. The bearings of the spindles have to be positioned relative to one another with great accuracy, so that the washing cloth runs exactly at right angles to the spindles and over the pressure element, by means of which in each case a cloth portion can be pressed onto the outer surface of the printing machine cylinder to be cleaned. Furthermore, care must be taken to ensure that the press-on pressure of the cloth is equal over the entire cylinder length. The production of the locating bores in the side parts and the production of the bearing elements consisting of the bearing bush and flange are costly.
The invention is intended to achieve the object of designing the bearing arrangements of the spindles in such a way that they can be produced in a shorter time and more cost-effectively, without avoiding sufficient accuracy in the positioning of the bearings.
This object is achieved, according to the invention.
A cleaning device for printing machine cylinders according to the invention has at least one of the bearings with a bearing bush which is provided with an external thread. It, therefore, can be screwed into an internal thread of the respective side part. An inner bearing part, which is designed for receiving a spindle end to be carried by the part, extends axially at least partially through the bearing bush and is positioned in the bearing bush.
The invention makes it simpler and less expensive to produce and assemble the cleaning device and reduces the production time and assembly time.
The invention is suitable, in particular, for cleaning of rubber-blanket cylinders in offset printing machines with a dry cleaning cloth or for washing with a moist washing cloth, but it may also be used for the cleaning of other cylinders in offset printing machines and in other types of printing machines.